<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>

var arr = [1, 2,[3, 4,[5,6,[7,8,[9,10],[11,12],[13,14,[15,16,[17,18]]]]]]]

 function deepClone(arr){

    let temp = []
    for(var i = 0;i < arr.length;i++){
        let item = arr[i]

        if(Array.isArray(item)){
            temp.push(deepClone(item)) 
        }else{
            temp.push(item) 
        }
    }

    return temp;

 }

 let newarr = deepClone(arr)

 newarr[2][0] = "hello"

 console.log(arr)
 console.log(newarr)

    </script>
</body>
</html>